Test Center: SANs tuned for virtualization pack nice surprises
Compellent, Dell, HP, Pillar Data, and roll-your-own Pillar/DataCore bring strong storage management features to XenServer, VMware, and Hyper-V environments
Compellent has another unique feature: the white-space recovery tool. Windows' NTFS is constructed to write new files to any unused blocks on disk before writing over blocks that have been freed up by deleting files. This doesn't matter on a normal hard disk, but will cause thin-provisioned virtual volumes to quickly expand to their maximum capacity. Compellent's recovery tool searches for blocks that are part of deleted files and marks them as unused so that Windows will overwrite them rather than using up all available space, thus ensuring that volumes don't expand unnecessarily.
Compellent Storage Center offers a great combination of capacity, high performance, and sophisticated features, making it hard to beat, whether for a traditional SAN environment or when specifically supporting virtualization. It's not the cheapest, but if you want to run a lot of VMs with both good performance and fault tolerance, it's an excellent choice.
Dell EqualLogic PS4000
Dell has a wide variety of storage systems, from simple direct-attached SCSI boxes to the EqualLogic iSCSI systems and Fibre Channel storage. The EqualLogic PS4000 is a very usable iSCSI system that starts at around $10,000, with 16 250GB SATA drives. Its predecessor, the PS3800, won InfoWorld's 2008 Technology of the Year Award for Best iSCSI SAN.
I received two PS4000 systems, both with dual controllers and dual power supplies, at a cost of $17,000 each as tested. Each controller has two gigabit Ethernet ports for iSCSI and a management port. The systems are available with up to 16 drives, which can be 7,200-rpm SATA, 10,000-rpm SAS, or 15,000-rpm SAS drives.
After installing the first PS4000, adding the second one was simply a matter of turning it on. The admin console found the second system, added it to the pool of available storage, and was ready to load balance across both units very quickly.
The PS4000 offers a great feature set included at the base price, with the usual thin provisioning, snapshots, replication, and load balancing across multiple iSCSI ports and multiple arrays to optimize performance. Creating new volumes and setting up options like replication is very straightforward. Coalescing multiple snapshots into a new volume was quick and easy.
The PS4000 offers an inexpensive starting price, a nice feature set, and the ability to grow in both capacity and performance by adding relatively inexpensive additional systems.